AN UNSTABLE FRAGMENT PRODUCED ON THE NUCLEAR CAPTURE OF A HYPERON

An event is described which consists in a slow singly charged particle of superprotonic mass, coming to rest in the emulsion and giving rise to an excited fragment and no other visible secondary; after a range of 46 μm, the fragment disintegrates into a proton of 110 MeV and singly charged particle with a range of 300 μm, which may be either a proton or a deuteron. The event is consistent with the assumption that a negative hyperon captured by a nucleus interacts according to the reaction Σ- + p → Λ∘ + n, the Λ∘ remaining bound into an unstable nuclear fragment, all other hyperon capture events known up to now are discussed in order to see if they could be interpreted as being due to the same reaction.